Rotary converter.



V. A. FYNN.

ROTARY CONVERTER.

APPLICATION FILED MAY 23, 1911.

1,044,641 Patented Nov. 19, 1912.

2 SHEET S-SHEET 1.

Fig.1.

WITNESSES: INVENTOR p I Valre A. Fynn,

BY 5 I 1 m 041/,

ROTARY CONVERTER APPLICATION FILED MAY 23, 1911.

1,044,641 Patented Nova 19, 1M2v 2 SHEETS-S11E31 2.

WITNESSES. INVENTOR C V fiire ANFyrm,

VALERIE ALFRED FYNN, BF LONDON, ENGLAND.

RGTARY CONVERTER.

Specification of Letter: Patent. Application filed May 23, 1911.

Patented Nov. 19, 1912. ierial No. 628,900.

To all whom it may concern. Be it known that I FYNN, a subject of theresiding at London, England, have invented a certain new and usefulRotary Converter, of which the following is such a full, clear, andexact description as will enable any one skilled in the art to which itappertains to make and use the same, reference being had to theaccompanying drawings, forming part of this specification.

y invention relates to improved. means for starting rotary convertersand has particular reference to single phase converters intended to bestarted from the alternat ing current side.

It is well known that such machines are very difiicult to start, andalthough a num ber of successful schemes have been proposed the allinvolve the use of the commutator fbr the purpose of starting andtherefore necessitate a somewhat complicated change in the connectionsbefore the machine is ready to convert alternating into direct current,or vice versa. Furthermore such changes have always been made by hand.According to this invention I reduce the switching operations to aminimum, do not rel on the commutator for theproduction o a startingtorque, and provide novel, electrically operated and automatic means forchanging from the starting to the running connections.

y invention will be better understood by VALERE ALFRED reference to theaccompanying diagrammatic drawings representing a 2-pole converter inwhich-- Figure 1 shows the preferred scheme of connections, while Fig. 2illustrates the preferred mechanical construction of the mag neticcircuit and indicates the space location of the several stator and rotorwindings.

v It will be convenient for the purpose of description tosimultaueouslyrefer to both figures of the drawing, since Fig. 2 is merely a detailedpresentation of some of the parts diagrammatically indicated in Fig. 1.

The rotor 34 carries two windings, the main winding 2 which is connectedto a commutator and to the slip rings 5 and 6,

and an auxiliary winding 3 connected at one end to the slip ring 5 andat the other to an independent slip ring at. The main winding 2 is ofthe commuted type and is uniformly distributed over the whole rotorcircumference, conductors belonging to said winding being placed in eachof the rotor King of England,

ing is shown as slots 35. The auxiliary winding 3 is distributed over apart only of the rotor circun'iference, being placed in only a few ofthe rotor slots, as shown in Fig. 2. This auxiliary winding is only usedduring the starting period and may therefore consist of a comparativelythin wire. Connection between the slip rings and the outer circuits ismade in the usual manner by way of the brushes 7.8 and 9. Brushes l0 and11 rest on the commuted winding 2 or on the commutator belonging to saidwinding and are connected to the shunt exciting winding 15 disposed onthe stator and displaced by about 90 electrical degrees with respect tothe brush line 10-11. The stator also carries a polyphase shortcircuitedwinding which may be of the squirrel cage type. In Fig. 1 thisshort-circuited winda three phase winding l2 l3-l4,- while Fig. 2indicates a squirrel cage winding 36 in place thereof. A regulatingresistance 16 controlled by the switch 17 is provided in the shuntexciting circuit. The slip ring 5 connected to the main rotor winding isalso connected by way of the brush 8 to point 37 of themain switch 20.The other slip ring 6 connected to the main rotor winding is connectedto point 38 of the main switch 20 by way of the brush 9 and the ohmicresistance 18. The auxiliary slip ring 4 is connected to point 88 of themain switch 20 by way of the brush 7, the contacts 29-28 of theautomatic switch and the impedance 19.

The automatic switch just referred to consists of an electromagnetconnected in parallel to the commutator brushes 1011 and controlling anarmature 30, which is normally held in contact with the points 29 and 28by means of the spring 31, but which when attracted by the clectromngnet25 leaves the points 29-28 and connects the points 26 and 27. The mainswitch 20 merely connects the adjustable ratio transformer 21 to thecontacts 37 and 28. The primary of the transformer 21 is connected tothe mains 2324.

, ables the machine 'speed the periodicity main rotor winding 2, theauxiliary rotor winding 3, the ohmic resistance 18 and the impedance 19,with the polyphase short-circuited winding 1213-1 & of the stator entostart with a sufiiciently powerful torque, the machine then operating asa split-phase motor. The voltage appearing at the commutator brushes1011 will be an alternating voltage of the full periodicity of thesupply as long as the ma.- chine is at rest. As the machine gathers ofthat voltage will gradually diminish, and when the machine has reached asynchronous speed the voltage at the brushes 1011 will beuni-directional and its order of magnitude will be very near that whichit has in normal operation.

make use of this variation in the nature and magnitude of this voltagefor operating my automatic switch. In order to make the automatic switch25 suitably responsiveto the voltage appearing at brushes and impressedon the winding of its electromagnet 25, I make themagnetic circuit ofsaid switch of laminated iron and provide its coil 25 with a largenumber of turns for the purpose of increasing the impedance of theautomatic switch to such an extent that an alternating E. M. F. of lineperiodicity will be unable to send an appreciable current through theelectromagnet 25 and will consequently be unable to attract the armature30. The dimensioning of the electromagnet in the manner described will,however, not prevent a uni-directional E. M. F. or one of a very lowperiodicity from sending through said magnet a cur rent, the magnitudeof which is only or mainly determined by the ohmic resistance of thecircuit. I consequently select that ohmic resistance of the circuit insuch a way hat the E. M. F. available at the brushes TKO-11 at the timewhen the machine reaches a speed in the neighborhood of the synchronousis amply suflicient to attract the armature 30, thus interrupting theauxiliary or starting circuit containing the impedance 19 andshort-circuiting the ohmic resistance 18 in circuit with the main slipring 6 at starting. It is seen that the use of the automatic switchdescribed, reduces the necessary manipulations to the closing of themain switch 20 since the shunt switch 17 may, as has already beenpointed out, be closed before the converter is started. Should thisshunt switch not be closed before the converter is started then themachine will run up to speed as before and the automatic switch willoperate in the manner described, but the converter will not be in aposition to deliver direct current to the mains 40-41 until the shuntswitch hasbeen closed. This shunt switch can also be utithe vcommutator.

lized for the purpose of adjusting the power factor of the converter.

My invention in its broadest aspect, there fore, consists of the use inconnection with a rotary converter, of an automatic switch controlled byan electromagnet connected to a winding on the converter and responsiveonly at speeds in the neighborhood of the synchronous, said switch beingmade use of for the purpose of changing the starting connectionsto therunning connect-ions. As applied to a single phase converter my invention consists of a special arrangement of rotor windings which may becombined with the automatic switch herein described.

ticular embodiment of My invention is of course applicable to machineswith any number of pole pairs.

I do not wish to limit myself to the parmy invention as hereindescribed, but aim to cover by means of the appended claims all themodifications which fall within the scope of said invention.

Having fully described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is:

'1. In a rotary converter, the combination with a stator, of a'rotorprovided with a commuted winding and another winding distributed over apart only of the rotor circumference, two slip-rings connected to thecommuted winding, and a third slip-ring connected to the other rotorwinding.

2. In a rotary converter, the combination with an alternating currentsource, of a stator, a rotor provided-with a commuted winding andanother windin distributed over a part only of the rotor circumference,

.a commutator, two slip rings connected to the commuted winding, oneslip ring connected to the other rotor winding, and phase displacingdevices connected to the source and to the slip rings. 3. In a rotaryconverter, the combination with an alternating current source, of astator, a rotor provided with a commute winding and another windingdistributed over a part only of the rotor circumference, a commutator,two slip rings connected to the commuted winding, one slip ringconnected to the other rotor winding, phase displacingdevices connectedto the source an to the slip rings, and an automatic switch operated bya current derived from the converter for rendering the phase displacingdevices inoperative. v

In testimony whereof, I have hereunto set my hand and affixed my seal inthe presence of the two subscribing witnesses.

VALERIE ALFRED. FYNN. [as] Witnesses:

W. A. Annxaiimnn, ELIZABETH BATLEY.

